This invention relates to programmable logic device integrated circuits, and more particularly, to voltage regulator circuitry for producing a fixed internal power supply voltage from a range of potential external supply voltages.
Programmable logic devices are a type of integrated circuit that can be customized by a user to implement a desired logic design. In a typical scenario, a logic designer uses a logic design system to design a logic circuit. The logic design system uses information on programmable logic device hardware capabilities to help the designer implement the logic circuit. The logic design system creates configuration data. When the configuration data is loaded into the programmable logic device, it programs the logic of the programmable logic device so that the programmable logic device implements the designer's logic circuit.
Modern high performance programmable logic devices sometimes use multiple power supply voltages. A relatively large power supply voltage (e.g., 3.3 volts) may be used to power input-output circuits at the periphery of the device. Using a large power supply voltage for the input-output circuits ensures that these circuits will be able to operate at high speeds, will be able to interface with high-voltage logic on other chips, and will exhibit good noise tolerance.
A relatively low power supply voltage (e.g., 1.8 volts) may be used to power so-called core logic. The core logic on a programmable logic device generally is located in the center of the device and is operated at a relatively low power supply voltage to ensure high-speed low-power-consumption operation.
Depending on the architecture used for the programmable logic device, the device may also have regions of interface logic that operate at intermediate power supply voltages (e.g., 2.5 volts). This logic may serve as an interface between the low-voltage core logic and high-voltage I/O circuits.
Although there are important performance benefits involved in using multiple power supply voltages in a programmable logic device, some system designers may not be able to easily accommodate complex power supply voltage requirements. For example, if a system is being designed that uses 3.3 volt power for all of its major components, it may be burdensome for the system designer to add extra circuitry to produce a 1.8 volt power supply to accommodate a programmable logic device. Unless the need is great enough, the designer will not be able to justify the additional components for producing the 1.8 volt power supply and will be forced to use a lower-performance programmable logic device that does not require a 1.8 volt supply to operate its core logic.
It would therefore be desirable to be able to provide integrated circuits such as programmable logic devices that do not require special core logic power supply voltages to power their core logic.